1. Technical Field
The present invention relates to an optical disc drive and method of managing and storing addresses of defective data blocks on an optical disc, and more particularly, to an optical disc drive and method of managing and storing addresses of defective data blocks on an optical disc which creates a new defect table in the memory.
2. Description of the Prior Art
Optical discs, given their compact size, high capacity storage, and low price, have rapidly become one of the most dominant, non-volatile storage media in the contemporary information society. For example, the development of a DVD-RAM has made it possible for users to write data onto optical discs in accordance with their own specific needs, which affords the DVD-RAM a high degree of application flexibility.
It is necessary to have an optical disc drive before reading and writing data onto an optical disc. Please refer to FIG. 1 that shows a conventional optical disc drive 10. The optical disc drive 10 comprises a holder plate 14 to carry an optical disc 22, a motor 12 that drives the holder plate 14, a read/write head 16 that accesses data on the optical disc 22, a control circuit 18 that controls the operation of the optical disc drive 10, and a memory 20, such as Dynamic Random Access Memory (DRAM), that serves as a temporary storage device to record all relevant data during the operation of the control circuit 18.
The data on the optical disc 22 is recorded sequentially onto a track 24 through pit and land markings. It should be noted that for different kinds of optical discs, the schemes of recording the pit and land markings are different. Taking the DVD-RAM disc for example, a phase change technique is adopted to record pits and lands. In other words, data recording scheme applied to the DVD-RAM disc is similar to that applied to the CD-RW disc. When the optical disc drive 10 is ready to write data onto the optical disc 22, first the optical disc drive 10 stores the intended data in the memory 20 before writing the intended data onto the optical disc 22. The pick-up head 16 meanwhile checks for defects in the optical disc 22, and passes the check results back to control circuit 18.
Often due to defects stemming from scratch marks, change of material properties, or interference by micro-dust, data cannot be written onto the optical disc 22. To improve the reliability of an optical disc (e.g., a DVD-RAM disc), the information technology industry has committed itself to research and development optical disc defect management. When certain areas of the optical disc contain a defect that renders that area unsuitable for data storage, the DVD-RAM format redirects the target data for storage to a usable area.
When the optical disc drive 10 tries to access data on the optical disc 22, it temporarily loads the created defect table of the optical disc 22 into the memory 20. DT is hereinafter used to refer to the defect table of the optical disc 22 and as is well known the DVD-RAM optical disc contains two DTs that will be described in detail later. When the optical disc drive 10 tries to access data on the optical disc 22, the optical disc drive 10 uses the address of each data block to access the data it desires. If a data block is defective, the optical disc drive 10 then enlists the help of the DT to locate the replacement data block that stores the user data. In this manner, even with defects on the optical disc 22, the optical disc 22 still can store data for read-out.
On the other hand, the optical disc drive 10 writing data onto the optical disc 22 requires updating the DT in temporary storage in memory 20 accordingly. For instance, assume that during the write-in the optical disc drive 10 discovers a new defect on the optical disc 22 during a formatting stage or a writing data stage. The optical disc drive 10 directly inserts an entry corresponding to the new defect into the DT buffered in the memory 20 in defective address order (i.e., based on the address of the defect). The details of this operation are well known to those of average skill in this art and are therefore omitted herein for the sake of brevity. Later, when the optical disc drive 10 stops accessing data on the optical disc 22 the optical disc drive 10 writes the updated DT from the memory 20 onto the optical disc 22. For example, the optical disc drive 10 will stop access data on the optical disc 22 when the optical disc 22 is ejected at the conclusion of the formatting stage or the writing stage. This updated DT provides the reference that the optical disc drive 10 needs when it tries to access data on the optical disc 22 the next time around.
Please refer to FIG. 2 in conjunction with FIG. 3. FIG. 2 is a diagram illustrating a primary defect list (PDL) table 26 of the optical disc 20 according to the related art, and FIG. 3 is a diagram illustrating a secondary defect list (SDL) table 28 of the optical disc 20 according to the related art. Notice that for DVD-RAM disc the entries of the PDL table 26 are each four bytes that are composed of the following information and in parentheses the corresponding size required to store that information: PDL type (1 byte) and defective address (3 bytes). Also, notice that in the SDL table 28 the entries are each eight bytes that are composed of the following information and in parentheses the corresponding size required to store that information: SDL type (1 byte), defective address (3 bytes), reserve byte (1 byte), and replacement address (3 bytes). Regardless of their locations, the entries of the PDL table 26 and the SDL table 28 are sorted according to the addresses of the defective data blocks with which they correspond. For example, the defective data blocks can be sorted in an ascending order such as PDL entry 0<PDL entry 1<PDL entry 2<PDL entry P<FFFFFFFF. Please note that FFFFFFFF indicates the end of the PDL table 26. However, there may not exist any specific order among the corresponding addresses of the data blocks that are utilized in place of defective data blocks. In general, the PDL table 26 is used for recording defect entries during the formatting stage, while the SDL table 28 is used for recording defects during the data writing stage.
As mentioned earlier, if the optical disc drive 10 uncovers a defective data block during the write-in stage, the optical disc drive 10 replaces the defective data block with another data block (e.g., an available spare block) and updates the SDL table 28 that is temporarily stored in the memory 20 so that the updated SDL table 28 reflects the latest linkage between the defective blocks and the replacement data blocks.
It is apparent that this related art defect management method is inefficient as it results in unnecessary modifications to the PDL table 26 or the SDL table 28 in the memory 20 and the frequently executed sort operation will degrade performance of the memory 20. Therefore, it is apparent that new and improved methods and devices are needed.